It is well known that several mechanical operations must be performed in order to change a tire on an automobile or other similar vehicle. Typically, the wheel cover is detached from the wheel rim, the lug nuts are loosened, and after the vehicle is raised, the lug nuts are removed and the wheel assembly separated from its mounting. When the wheel assembly is to be returned or a replacement assembly mounted, the procedure is reversed. Thus, the assembly is placed on the mounting so that the wheel bolts extend through the holes in the wheel, the lug nuts are started and drawn tight on the wheel bolts, and after lowering the vehicle, the wheel cover is replaced. Essentially, these same operations are performed when the wheel assembly is removed and replaced for any other purpose in addition to changing the tire.
During the course of performance of these operations, several tools are generally employed, and particularly when the wheel assembly is not replaced in a shop or service station, the tools are manually operated rather than power driven. For example, a screwdriver is often used to pry the wheel cover from the rim by wedging its end between the cover and rim and levering the cover from its attached position. The wheel cover can then be replaced by holding the cover against the rim and hammering it in place with a rubber-headed mallet. The latter operation, however, is more often performed by hitting the wheel cover with the palm of the hand since rubber-headed mallets are not normally carried in vehicles for emergency or owner use.
In the absence of power driven tools, the lug nuts are ordinarily loosened and tightened with a wrench having at one end a socket which is adapted to receive lug nuts of the corresponding size. One commonly known wrench comprises four perpendicular arms which are rigidly secured to each other to form an X-shaped tool. The arms are generally provided with sockets of different sizes so that a standard lug nut can be turned on a wheel bolt by rotating the tool about the longitudinal axis of two opposing arms while retaining the lug nut in the socket of one of the opposing arms. This particular tool, however, provides only the means for removing or replacing lug nuts when changing the wheel assembly. Furthermore, its awkward size and configuration makes storage difficult, and therefore, the tool is not usually carried in the vehicle.
To alleviate the storage problem, there has been proposed a collapsible wrench which includes two arms that are pivotally joined at their centers in a crossing relationship. During usage, the arms are held in a perpendicular position for rotating the tool in the usual manner, and for storage, the arms can be brought together in substantially a parallel relationship. Typically, the arms are joined with a screw member or bolt which passes through the longitudinal center of the arms. A nut is then placed on the end of the bolt to secure the arms in the perpendicular position by clamping the arms together. The bolt furthermore provides means for transmitting torque between the members and is subject to a bending torque and tensile stress when applied to securely fastened lug nuts.
As illustrated in U.S. Pat. No. 3,587,366 to Klein, wrenches have been designed to reduce the bending torque applied to the joining bolt by introducing a coupling between the arms to distribute the torsional forces along the arms. However, even if the arms are securely fastened, stress is still applied to the bolt which can eventually break due to metal fatique. In addition, it would appear that since the joining bolt and nut are repeatedly loosened and tightened, wear on the threads of the joining bolt would be inevitable.
To clamp the arms of typical collapsible wrenches, the operator must hold the two arms in position with one hand while operating the joining bolt and nut with the other. This presents not only a cumbersome and awkward operation, but also there is a danger that the operator's hand or fingers will be pinched by the closely positioned arms or associated joining members. Furthermore, since the joining bolt and nut are ordinarily retained in a loose position when not in use, it would appear that the arms could be easily disconnected and the components inadvertently misplaced.